1 //! Methods for lowering the HIR to types. There are two main cases here:
3 //! - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
4 //! type: The entry point for this is `Ty::from_hir`.
5 //! - Building the type for an item: This happens through the `type_for_def` query.
7 //! This usually involves resolving names, collecting generic arguments etc.
8 use std::{iter, sync::Arc};
11 use chalk_ir::{cast::Cast, Mutability, Safety};
14 builtin_type::BuiltinType,
15 generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
16 path::{GenericArg, Path, PathSegment, PathSegments},
17 resolver::{HasResolver, Resolver, TypeNs},
18 type_ref::{TypeBound, TypeRef},
19 AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
20 GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
21 TypeAliasId, TypeParamId, UnionId, VariantId,
23 use hir_expand::name::Name;
24 use la_arena::ArenaMap;
25 use smallvec::SmallVec;
30 to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
31 traits::chalk::{Interner, ToChalk},
33 all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
36 AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
37 ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause, QuantifiedWhereClauses,
38 ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution, TraitEnvironment, TraitRef, Ty,
39 TyKind, TypeWalk, WhereClause,
43 pub struct TyLoweringContext<'a> {
44 pub db: &'a dyn HirDatabase,
45 pub resolver: &'a Resolver,
46 in_binders: DebruijnIndex,
47 /// Note: Conceptually, it's thinkable that we could be in a location where
48 /// some type params should be represented as placeholders, and others
49 /// should be converted to variables. I think in practice, this isn't
50 /// possible currently, so this should be fine for now.
51 pub type_param_mode: TypeParamLoweringMode,
52 pub impl_trait_mode: ImplTraitLoweringMode,
53 impl_trait_counter: std::cell::Cell<u16>,
54 /// When turning `impl Trait` into opaque types, we have to collect the
55 /// bounds at the same time to get the IDs correct (without becoming too
56 /// complicated). I don't like using interior mutability (as for the
57 /// counter), but I've tried and failed to make the lifetimes work for
58 /// passing around a `&mut TyLoweringContext`. The core problem is that
59 /// we're grouping the mutable data (the counter and this field) together
60 /// with the immutable context (the references to the DB and resolver).
61 /// Splitting this up would be a possible fix.
62 opaque_type_data: std::cell::RefCell<Vec<ReturnTypeImplTrait>>,
65 impl<'a> TyLoweringContext<'a> {
66 pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
67 let impl_trait_counter = std::cell::Cell::new(0);
68 let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
69 let type_param_mode = TypeParamLoweringMode::Placeholder;
70 let in_binders = DebruijnIndex::INNERMOST;
71 let opaque_type_data = std::cell::RefCell::new(Vec::new());
83 pub fn with_debruijn<T>(
85 debruijn: DebruijnIndex,
86 f: impl FnOnce(&TyLoweringContext) -> T,
88 let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
91 impl_trait_counter: std::cell::Cell::new(self.impl_trait_counter.get()),
92 opaque_type_data: std::cell::RefCell::new(opaque_ty_data_vec),
95 let result = f(&new_ctx);
96 self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
97 self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
101 pub fn with_shifted_in<T>(
103 debruijn: DebruijnIndex,
104 f: impl FnOnce(&TyLoweringContext) -> T,
106 self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
109 pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
110 Self { impl_trait_mode, ..self }
113 pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
114 Self { type_param_mode, ..self }
118 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
119 pub enum ImplTraitLoweringMode {
120 /// `impl Trait` gets lowered into an opaque type that doesn't unify with
121 /// anything except itself. This is used in places where values flow 'out',
122 /// i.e. for arguments of the function we're currently checking, and return
123 /// types of functions we're calling.
125 /// `impl Trait` gets lowered into a type variable. Used for argument
126 /// position impl Trait when inside the respective function, since it allows
127 /// us to support that without Chalk.
129 /// `impl Trait` gets lowered into a variable that can unify with some
130 /// type. This is used in places where values flow 'in', i.e. for arguments
131 /// of functions we're calling, and the return type of the function we're
132 /// currently checking.
134 /// `impl Trait` is disallowed and will be an error.
138 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
139 pub enum TypeParamLoweringMode {
144 impl<'a> TyLoweringContext<'a> {
145 pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
146 self.lower_ty_ext(type_ref).0
149 fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
151 let ty = match type_ref {
152 TypeRef::Never => TyKind::Never.intern(&Interner),
153 TypeRef::Tuple(inner) => {
154 let inner_tys = inner.iter().map(|tr| self.lower_ty(tr));
155 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
158 TypeRef::Path(path) => {
159 let (ty, res_) = self.lower_path(path);
163 TypeRef::RawPtr(inner, mutability) => {
164 let inner_ty = self.lower_ty(inner);
165 TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
167 TypeRef::Array(inner) => {
168 let inner_ty = self.lower_ty(inner);
169 TyKind::Array(inner_ty).intern(&Interner)
171 TypeRef::Slice(inner) => {
172 let inner_ty = self.lower_ty(inner);
173 TyKind::Slice(inner_ty).intern(&Interner)
175 TypeRef::Reference(inner, _, mutability) => {
176 let inner_ty = self.lower_ty(inner);
177 TyKind::Ref(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
179 TypeRef::Placeholder => TyKind::Unknown.intern(&Interner),
180 TypeRef::Fn(params, is_varargs) => {
181 let substs = Substitution(params.iter().map(|tr| self.lower_ty(tr)).collect());
182 TyKind::Function(FnPointer {
183 num_args: substs.len() - 1,
184 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
189 TypeRef::DynTrait(bounds) => {
191 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
192 let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
193 QuantifiedWhereClauses::from_iter(
195 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
198 let bounds = Binders::new(1, bounds);
199 TyKind::Dyn(DynTy { bounds }).intern(&Interner)
201 TypeRef::ImplTrait(bounds) => {
202 match self.impl_trait_mode {
203 ImplTraitLoweringMode::Opaque => {
204 let idx = self.impl_trait_counter.get();
205 self.impl_trait_counter.set(idx + 1);
207 assert!(idx as usize == self.opaque_type_data.borrow().len());
208 // this dance is to make sure the data is in the right
209 // place even if we encounter more opaque types while
210 // lowering the bounds
211 self.opaque_type_data
213 .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
214 // We don't want to lower the bounds inside the binders
215 // we're currently in, because they don't end up inside
216 // those binders. E.g. when we have `impl Trait<impl
217 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
218 // to the self parameter from `impl Trait`, and the
219 // bounds aren't actually stored nested within each
220 // other, but separately. So if the `T` refers to a type
221 // parameter of the outer function, it's just one binder
222 // away instead of two.
223 let actual_opaque_type_data = self
224 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
225 ctx.lower_impl_trait(&bounds)
227 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
229 let func = match self.resolver.generic_def() {
230 Some(GenericDefId::FunctionId(f)) => f,
231 _ => panic!("opaque impl trait lowering in non-function"),
233 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
234 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
235 let generics = generics(self.db.upcast(), func.into());
236 let parameters = Substitution::bound_vars(&generics, self.in_binders);
237 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
239 substitution: parameters,
243 ImplTraitLoweringMode::Param => {
244 let idx = self.impl_trait_counter.get();
245 // FIXME we're probably doing something wrong here
246 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
247 if let Some(def) = self.resolver.generic_def() {
248 let generics = generics(self.db.upcast(), def);
251 .filter(|(_, data)| {
252 data.provenance == TypeParamProvenance::ArgumentImplTrait
255 .map_or(TyKind::Unknown, |(id, _)| {
256 TyKind::Placeholder(to_placeholder_idx(self.db, id))
258 param.intern(&Interner)
260 TyKind::Unknown.intern(&Interner)
263 ImplTraitLoweringMode::Variable => {
264 let idx = self.impl_trait_counter.get();
265 // FIXME we're probably doing something wrong here
266 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
267 let (parent_params, self_params, list_params, _impl_trait_params) =
268 if let Some(def) = self.resolver.generic_def() {
269 let generics = generics(self.db.upcast(), def);
270 generics.provenance_split()
274 TyKind::BoundVar(BoundVar::new(
276 idx as usize + parent_params + self_params + list_params,
280 ImplTraitLoweringMode::Disallowed => {
281 // FIXME: report error
282 TyKind::Unknown.intern(&Interner)
286 TypeRef::Error => TyKind::Unknown.intern(&Interner),
291 /// This is only for `generic_predicates_for_param`, where we can't just
292 /// lower the self types of the predicates since that could lead to cycles.
293 /// So we just check here if the `type_ref` resolves to a generic param, and which.
294 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
295 let path = match type_ref {
296 TypeRef::Path(path) => path,
299 if path.type_anchor().is_some() {
302 if path.segments().len() > 1 {
306 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
307 Some((it, None)) => it,
310 if let TypeNs::GenericParam(param_id) = resolution {
317 pub(crate) fn lower_ty_relative_path(
320 // We need the original resolution to lower `Self::AssocTy` correctly
322 remaining_segments: PathSegments<'_>,
323 ) -> (Ty, Option<TypeNs>) {
324 if remaining_segments.len() == 1 {
325 // resolve unselected assoc types
326 let segment = remaining_segments.first().unwrap();
327 (self.select_associated_type(res, segment), None)
328 } else if remaining_segments.len() > 1 {
329 // FIXME report error (ambiguous associated type)
330 (TyKind::Unknown.intern(&Interner), None)
336 pub(crate) fn lower_partly_resolved_path(
339 resolved_segment: PathSegment<'_>,
340 remaining_segments: PathSegments<'_>,
342 ) -> (Ty, Option<TypeNs>) {
343 let ty = match resolution {
344 TypeNs::TraitId(trait_) => {
345 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
346 let self_ty = if remaining_segments.len() == 0 {
348 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
355 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
356 let ty = if remaining_segments.len() == 1 {
357 let segment = remaining_segments.first().unwrap();
358 let found = associated_type_by_name_including_super_traits(
364 Some((super_trait_ref, associated_ty)) => {
365 // FIXME handle type parameters on the segment
366 TyKind::Alias(AliasTy::Projection(ProjectionTy {
367 associated_ty_id: to_assoc_type_id(associated_ty),
368 substitution: super_trait_ref.substitution,
373 // FIXME: report error (associated type not found)
374 TyKind::Unknown.intern(&Interner)
377 } else if remaining_segments.len() > 1 {
378 // FIXME report error (ambiguous associated type)
379 TyKind::Unknown.intern(&Interner)
382 bounds: Binders::new(
384 QuantifiedWhereClauses::from_iter(
386 Some(Binders::wrap_empty(WhereClause::Implemented(trait_ref))),
390 TyKind::Dyn(dyn_ty).intern(&Interner)
394 TypeNs::GenericParam(param_id) => {
395 let generics = generics(
397 self.resolver.generic_def().expect("generics in scope"),
399 match self.type_param_mode {
400 TypeParamLoweringMode::Placeholder => {
401 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
403 TypeParamLoweringMode::Variable => {
404 let idx = generics.param_idx(param_id).expect("matching generics");
405 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
410 TypeNs::SelfType(impl_id) => {
411 let generics = generics(self.db.upcast(), impl_id.into());
412 let substs = match self.type_param_mode {
413 TypeParamLoweringMode::Placeholder => {
414 Substitution::type_params_for_generics(self.db, &generics)
416 TypeParamLoweringMode::Variable => {
417 Substitution::bound_vars(&generics, self.in_binders)
420 self.db.impl_self_ty(impl_id).subst(&substs)
422 TypeNs::AdtSelfType(adt) => {
423 let generics = generics(self.db.upcast(), adt.into());
424 let substs = match self.type_param_mode {
425 TypeParamLoweringMode::Placeholder => {
426 Substitution::type_params_for_generics(self.db, &generics)
428 TypeParamLoweringMode::Variable => {
429 Substitution::bound_vars(&generics, self.in_binders)
432 self.db.ty(adt.into()).subst(&substs)
435 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
436 TypeNs::BuiltinType(it) => {
437 self.lower_path_inner(resolved_segment, it.into(), infer_args)
439 TypeNs::TypeAliasId(it) => {
440 self.lower_path_inner(resolved_segment, it.into(), infer_args)
442 // FIXME: report error
443 TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
445 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
448 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
449 // Resolve the path (in type namespace)
450 if let Some(type_ref) = path.type_anchor() {
451 let (ty, res) = self.lower_ty_ext(&type_ref);
452 return self.lower_ty_relative_path(ty, res, path.segments());
454 let (resolution, remaining_index) =
455 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
457 None => return (TyKind::Unknown.intern(&Interner), None),
459 let (resolved_segment, remaining_segments) = match remaining_index {
461 path.segments().last().expect("resolved path has at least one element"),
464 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
466 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
469 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
470 if let Some(res) = res {
471 let ty = associated_type_shorthand_candidates(
474 move |name, t, associated_ty| {
475 if name == segment.name {
476 let substs = match self.type_param_mode {
477 TypeParamLoweringMode::Placeholder => {
478 // if we're lowering to placeholders, we have to put
480 let s = Substitution::type_params(
482 self.resolver.generic_def().expect(
483 "there should be generics if there's a generic param",
486 t.substitution.clone().subst_bound_vars(&s)
488 TypeParamLoweringMode::Variable => t.substitution.clone(),
490 // We need to shift in the bound vars, since
491 // associated_type_shorthand_candidates does not do that
492 let substs = substs.shift_bound_vars(self.in_binders);
493 // FIXME handle type parameters on the segment
495 TyKind::Alias(AliasTy::Projection(ProjectionTy {
496 associated_ty_id: to_assoc_type_id(associated_ty),
497 substitution: substs,
507 ty.unwrap_or(TyKind::Unknown.intern(&Interner))
509 TyKind::Unknown.intern(&Interner)
515 segment: PathSegment<'_>,
519 let generic_def = match typeable {
520 TyDefId::BuiltinType(_) => None,
521 TyDefId::AdtId(it) => Some(it.into()),
522 TyDefId::TypeAliasId(it) => Some(it.into()),
524 let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
525 self.db.ty(typeable).subst(&substs)
528 /// Collect generic arguments from a path into a `Substs`. See also
529 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
530 pub(super) fn substs_from_path(
533 // Note that we don't call `db.value_type(resolved)` here,
534 // `ValueTyDefId` is just a convenient way to pass generics and
535 // special-case enum variants
536 resolved: ValueTyDefId,
539 let last = path.segments().last().expect("path should have at least one segment");
540 let (segment, generic_def) = match resolved {
541 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
542 ValueTyDefId::StructId(it) => (last, Some(it.into())),
543 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
544 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
545 ValueTyDefId::StaticId(_) => (last, None),
546 ValueTyDefId::EnumVariantId(var) => {
547 // the generic args for an enum variant may be either specified
548 // on the segment referring to the enum, or on the segment
549 // referring to the variant. So `Option::<T>::None` and
550 // `Option::None::<T>` are both allowed (though the former is
551 // preferred). See also `def_ids_for_path_segments` in rustc.
552 let len = path.segments().len();
553 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
554 let segment = match penultimate {
555 Some(segment) if segment.args_and_bindings.is_some() => segment,
558 (segment, Some(var.parent.into()))
561 self.substs_from_path_segment(segment, generic_def, infer_args, None)
564 fn substs_from_path_segment(
566 segment: PathSegment<'_>,
567 def_generic: Option<GenericDefId>,
569 explicit_self_ty: Option<Ty>,
571 let mut substs = Vec::new();
572 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
574 let (parent_params, self_params, type_params, impl_trait_params) =
575 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
576 let total_len = parent_params + self_params + type_params + impl_trait_params;
578 substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
580 let fill_self_params = || {
584 .chain(iter::repeat(TyKind::Unknown.intern(&Interner)))
588 let mut had_explicit_type_args = false;
590 if let Some(generic_args) = &segment.args_and_bindings {
591 if !generic_args.has_self_type {
595 if generic_args.has_self_type { self_params + type_params } else { type_params };
596 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
597 // if args are provided, it should be all of them, but we can't rely on that
598 for arg in generic_args
601 .filter(|arg| matches!(arg, GenericArg::Type(_)))
606 GenericArg::Type(type_ref) => {
607 had_explicit_type_args = true;
608 let ty = self.lower_ty(type_ref);
611 GenericArg::Lifetime(_) => {}
618 // handle defaults. In expression or pattern path segments without
619 // explicitly specified type arguments, missing type arguments are inferred
620 // (i.e. defaults aren't used).
621 if !infer_args || had_explicit_type_args {
622 if let Some(def_generic) = def_generic {
623 let defaults = self.db.generic_defaults(def_generic);
624 assert_eq!(total_len, defaults.len());
626 for default_ty in defaults.iter().skip(substs.len()) {
627 // each default can depend on the previous parameters
628 let substs_so_far = Substitution(substs.clone().into());
629 substs.push(default_ty.clone().subst(&substs_so_far));
634 // add placeholders for args that were not provided
635 // FIXME: emit diagnostics in contexts where this is not allowed
636 for _ in substs.len()..total_len {
637 substs.push(TyKind::Unknown.intern(&Interner));
639 assert_eq!(substs.len(), total_len);
641 Substitution(substs.into())
644 fn lower_trait_ref_from_path(
647 explicit_self_ty: Option<Ty>,
648 ) -> Option<TraitRef> {
650 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
651 TypeNs::TraitId(tr) => tr,
654 let segment = path.segments().last().expect("path should have at least one segment");
655 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
658 pub(crate) fn lower_trait_ref_from_resolved_path(
661 segment: PathSegment<'_>,
662 explicit_self_ty: Option<Ty>,
664 let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
665 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
671 explicit_self_ty: Option<Ty>,
672 ) -> Option<TraitRef> {
673 let path = match type_ref {
674 TypeRef::Path(path) => path,
677 self.lower_trait_ref_from_path(path, explicit_self_ty)
680 fn trait_ref_substs_from_path(
682 segment: PathSegment<'_>,
684 explicit_self_ty: Option<Ty>,
686 self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
689 pub(crate) fn lower_where_predicate(
691 where_predicate: &'a WherePredicate,
692 ignore_bindings: bool,
693 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
694 match where_predicate {
695 WherePredicate::ForLifetime { target, bound, .. }
696 | WherePredicate::TypeBound { target, bound } => {
697 let self_ty = match target {
698 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
699 WherePredicateTypeTarget::TypeParam(param_id) => {
700 let generic_def = self.resolver.generic_def().expect("generics in scope");
701 let generics = generics(self.db.upcast(), generic_def);
703 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
704 let placeholder = to_placeholder_idx(self.db, param_id);
705 match self.type_param_mode {
706 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
707 TypeParamLoweringMode::Variable => {
708 let idx = generics.param_idx(param_id).expect("matching generics");
709 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
715 self.lower_type_bound(bound, self_ty, ignore_bindings)
719 WherePredicate::Lifetime { .. } => vec![].into_iter(),
723 pub(crate) fn lower_type_bound(
725 bound: &'a TypeBound,
727 ignore_bindings: bool,
728 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
729 let mut bindings = None;
730 let trait_ref = match bound {
731 TypeBound::Path(path) => {
732 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
733 bindings.clone().map(WhereClause::Implemented).map(|b| Binders::wrap_empty(b))
735 TypeBound::Lifetime(_) => None,
736 TypeBound::Error => None,
738 trait_ref.into_iter().chain(
741 .filter(move |_| !ignore_bindings)
742 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
746 fn assoc_type_bindings_from_type_bound(
748 bound: &'a TypeBound,
750 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
751 let last_segment = match bound {
752 TypeBound::Path(path) => path.segments().last(),
753 TypeBound::Error | TypeBound::Lifetime(_) => None,
757 .flat_map(|segment| segment.args_and_bindings.into_iter())
758 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
759 .flat_map(move |binding| {
760 let found = associated_type_by_name_including_super_traits(
765 let (super_trait_ref, associated_ty) = match found {
766 None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(),
769 let projection_ty = ProjectionTy {
770 associated_ty_id: to_assoc_type_id(associated_ty),
771 substitution: super_trait_ref.substitution,
773 let mut preds = SmallVec::with_capacity(
774 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
776 if let Some(type_ref) = &binding.type_ref {
777 let ty = self.lower_ty(type_ref);
779 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
780 preds.push(Binders::wrap_empty(WhereClause::AliasEq(alias_eq)));
782 for bound in &binding.bounds {
783 preds.extend(self.lower_type_bound(
785 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
793 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
794 cov_mark::hit!(lower_rpit);
796 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
797 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
798 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
800 ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
804 fn count_impl_traits(type_ref: &TypeRef) -> usize {
806 type_ref.walk(&mut |type_ref| {
807 if matches!(type_ref, TypeRef::ImplTrait(_)) {
814 /// Build the signature of a callable item (function, struct or enum variant).
815 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
817 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
818 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
819 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
823 pub fn associated_type_shorthand_candidates<R>(
824 db: &dyn HirDatabase,
826 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
828 let traits_from_env: Vec<_> = match res {
829 TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
831 Some(trait_ref) => vec![trait_ref.value],
833 TypeNs::GenericParam(param_id) => {
834 let predicates = db.generic_predicates_for_param(param_id);
835 let mut traits_: Vec<_> = predicates
837 .filter_map(|pred| match &pred.value.value {
838 WhereClause::Implemented(tr) => Some(tr.clone()),
842 // Handle `Self::Type` referring to own associated type in trait definitions
843 if let GenericDefId::TraitId(trait_id) = param_id.parent {
844 let generics = generics(db.upcast(), trait_id.into());
845 if generics.params.types[param_id.local_id].provenance
846 == TypeParamProvenance::TraitSelf
848 let trait_ref = TraitRef {
849 trait_id: to_chalk_trait_id(trait_id),
850 substitution: Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST),
852 traits_.push(trait_ref);
860 for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
861 let data = db.trait_data(t.hir_trait_id());
863 for (name, assoc_id) in &data.items {
865 AssocItemId::TypeAliasId(alias) => {
866 if let Some(result) = cb(name, &t, *alias) {
870 AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
878 /// Build the type of all specific fields of a struct or enum variant.
879 pub(crate) fn field_types_query(
880 db: &dyn HirDatabase,
881 variant_id: VariantId,
882 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
883 let var_data = variant_data(db.upcast(), variant_id);
884 let (resolver, def): (_, GenericDefId) = match variant_id {
885 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
886 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
887 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
889 let generics = generics(db.upcast(), def);
890 let mut res = ArenaMap::default();
892 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
893 for (field_id, field_data) in var_data.fields().iter() {
894 res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
899 /// This query exists only to be used when resolving short-hand associated types
902 /// See the analogous query in rustc and its comment:
903 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
904 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
905 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
906 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
907 pub(crate) fn generic_predicates_for_param_query(
908 db: &dyn HirDatabase,
909 param_id: TypeParamId,
910 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
911 let resolver = param_id.parent.resolver(db.upcast());
913 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
914 let generics = generics(db.upcast(), param_id.parent);
916 .where_predicates_in_scope()
917 // we have to filter out all other predicates *first*, before attempting to lower them
918 .filter(|pred| match pred {
919 WherePredicate::ForLifetime { target, .. }
920 | WherePredicate::TypeBound { target, .. } => match target {
921 WherePredicateTypeTarget::TypeRef(type_ref) => {
922 ctx.lower_ty_only_param(type_ref) == Some(param_id)
924 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
926 WherePredicate::Lifetime { .. } => false,
929 ctx.lower_where_predicate(pred, true).map(|p| Binders::new(generics.len(), p))
934 pub(crate) fn generic_predicates_for_param_recover(
935 _db: &dyn HirDatabase,
937 _param_id: &TypeParamId,
938 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
942 pub(crate) fn trait_environment_query(
943 db: &dyn HirDatabase,
945 ) -> Arc<TraitEnvironment> {
946 let resolver = def.resolver(db.upcast());
947 let ctx = TyLoweringContext::new(db, &resolver)
948 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
949 let mut traits_in_scope = Vec::new();
950 let mut clauses = Vec::new();
951 for pred in resolver.where_predicates_in_scope() {
952 for pred in ctx.lower_where_predicate(pred, false) {
953 if let WhereClause::Implemented(tr) = &pred.skip_binders() {
954 traits_in_scope.push((tr.self_type_parameter().clone(), tr.hir_trait_id()));
956 let program_clause: chalk_ir::ProgramClause<Interner> =
957 pred.clone().to_chalk(db).cast(&Interner);
958 clauses.push(program_clause.into_from_env_clause(&Interner));
962 let container: Option<AssocContainerId> = match def {
963 // FIXME: is there a function for this?
964 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
965 GenericDefId::AdtId(_) => None,
966 GenericDefId::TraitId(_) => None,
967 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
968 GenericDefId::ImplId(_) => None,
969 GenericDefId::EnumVariantId(_) => None,
970 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
972 if let Some(AssocContainerId::TraitId(trait_id)) = container {
973 // add `Self: Trait<T1, T2, ...>` to the environment in trait
974 // function default implementations (and hypothetical code
975 // inside consts or type aliases)
976 cov_mark::hit!(trait_self_implements_self);
977 let substs = Substitution::type_params(db, trait_id);
978 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
979 let pred = WhereClause::Implemented(trait_ref);
980 let program_clause: chalk_ir::ProgramClause<Interner> = pred.to_chalk(db).cast(&Interner);
981 clauses.push(program_clause.into_from_env_clause(&Interner));
984 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
986 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
989 /// Resolve the where clause(s) of an item with generics.
990 pub(crate) fn generic_predicates_query(
991 db: &dyn HirDatabase,
993 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
994 let resolver = def.resolver(db.upcast());
996 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
997 let generics = generics(db.upcast(), def);
999 .where_predicates_in_scope()
1001 ctx.lower_where_predicate(pred, false).map(|p| Binders::new(generics.len(), p))
1006 /// Resolve the default type params from generics
1007 pub(crate) fn generic_defaults_query(
1008 db: &dyn HirDatabase,
1010 ) -> Arc<[Binders<Ty>]> {
1011 let resolver = def.resolver(db.upcast());
1013 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1014 let generic_params = generics(db.upcast(), def);
1016 let defaults = generic_params
1019 .map(|(idx, (_, p))| {
1021 p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
1023 // Each default can only refer to previous parameters.
1024 ty.walk_mut_binders(
1025 &mut |ty, binders| match ty.interned_mut() {
1026 TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
1028 // type variable default referring to parameter coming
1029 // after it. This is forbidden (FIXME: report
1031 *ty = TyKind::Unknown.intern(&Interner);
1036 DebruijnIndex::INNERMOST,
1039 Binders::new(idx, ty)
1046 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1047 let data = db.function_data(def);
1048 let resolver = def.resolver(db.upcast());
1049 let ctx_params = TyLoweringContext::new(db, &resolver)
1050 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1051 .with_type_param_mode(TypeParamLoweringMode::Variable);
1052 let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
1053 let ctx_ret = TyLoweringContext::new(db, &resolver)
1054 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1055 .with_type_param_mode(TypeParamLoweringMode::Variable);
1056 let ret = (&ctx_ret).lower_ty(&data.ret_type);
1057 let generics = generics(db.upcast(), def.into());
1058 let num_binders = generics.len();
1059 Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
1062 /// Build the declared type of a function. This should not need to look at the
1064 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1065 let generics = generics(db.upcast(), def.into());
1066 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1069 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1073 /// Build the declared type of a const.
1074 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1075 let data = db.const_data(def);
1076 let generics = generics(db.upcast(), def.into());
1077 let resolver = def.resolver(db.upcast());
1079 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1081 Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
1084 /// Build the declared type of a static.
1085 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1086 let data = db.static_data(def);
1087 let resolver = def.resolver(db.upcast());
1088 let ctx = TyLoweringContext::new(db, &resolver);
1090 Binders::new(0, ctx.lower_ty(&data.type_ref))
1093 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1094 let struct_data = db.struct_data(def);
1095 let fields = struct_data.variant_data.fields();
1096 let resolver = def.resolver(db.upcast());
1098 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1099 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1100 let ret = type_for_adt(db, def.into());
1101 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1104 /// Build the type of a tuple struct constructor.
1105 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1106 let struct_data = db.struct_data(def);
1107 if let StructKind::Unit = struct_data.variant_data.kind() {
1108 return type_for_adt(db, def.into());
1110 let generics = generics(db.upcast(), def.into());
1111 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1114 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1118 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1119 let enum_data = db.enum_data(def.parent);
1120 let var_data = &enum_data.variants[def.local_id];
1121 let fields = var_data.variant_data.fields();
1122 let resolver = def.parent.resolver(db.upcast());
1124 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1125 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1126 let ret = type_for_adt(db, def.parent.into());
1127 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1130 /// Build the type of a tuple enum variant constructor.
1131 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1132 let enum_data = db.enum_data(def.parent);
1133 let var_data = &enum_data.variants[def.local_id].variant_data;
1134 if let StructKind::Unit = var_data.kind() {
1135 return type_for_adt(db, def.parent.into());
1137 let generics = generics(db.upcast(), def.parent.into());
1138 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1141 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1145 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1146 let generics = generics(db.upcast(), adt.into());
1147 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1148 Binders::new(substs.len(), Ty::adt_ty(adt, substs))
1151 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1152 let generics = generics(db.upcast(), t.into());
1153 let resolver = t.resolver(db.upcast());
1155 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1156 if db.type_alias_data(t).is_extern {
1157 Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
1159 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1160 let type_ref = &db.type_alias_data(t).type_ref;
1161 let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
1162 Binders::new(substs.len(), inner)
1166 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1167 pub enum CallableDefId {
1168 FunctionId(FunctionId),
1170 EnumVariantId(EnumVariantId),
1172 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1174 impl CallableDefId {
1175 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1176 let db = db.upcast();
1178 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1179 CallableDefId::StructId(s) => s.lookup(db).container,
1180 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1186 impl From<CallableDefId> for GenericDefId {
1187 fn from(def: CallableDefId) -> GenericDefId {
1189 CallableDefId::FunctionId(f) => f.into(),
1190 CallableDefId::StructId(s) => s.into(),
1191 CallableDefId::EnumVariantId(e) => e.into(),
1196 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1198 BuiltinType(BuiltinType),
1200 TypeAliasId(TypeAliasId),
1202 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1204 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1205 pub enum ValueTyDefId {
1206 FunctionId(FunctionId),
1209 EnumVariantId(EnumVariantId),
1213 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1215 /// Build the declared type of an item. This depends on the namespace; e.g. for
1216 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1217 /// the constructor function `(usize) -> Foo` which lives in the values
1219 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1221 TyDefId::BuiltinType(it) => Binders::new(0, Ty::builtin(it)),
1222 TyDefId::AdtId(it) => type_for_adt(db, it),
1223 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1227 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1228 let num_binders = match *def {
1229 TyDefId::BuiltinType(_) => 0,
1230 TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
1231 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
1233 Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
1236 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1238 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1239 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1240 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1241 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1242 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1243 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1247 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1248 let impl_data = db.impl_data(impl_id);
1249 let resolver = impl_id.resolver(db.upcast());
1250 let generics = generics(db.upcast(), impl_id.into());
1252 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1253 Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
1256 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1257 let parent_data = db.generic_params(def.parent);
1258 let data = &parent_data.consts[def.local_id];
1259 let resolver = def.parent.resolver(db.upcast());
1260 let ctx = TyLoweringContext::new(db, &resolver);
1262 ctx.lower_ty(&data.ty)
1265 pub(crate) fn impl_self_ty_recover(
1266 db: &dyn HirDatabase,
1270 let generics = generics(db.upcast(), (*impl_id).into());
1271 Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
1274 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1275 let impl_data = db.impl_data(impl_id);
1276 let resolver = impl_id.resolver(db.upcast());
1278 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1279 let self_ty = db.impl_self_ty(impl_id);
1280 let target_trait = impl_data.target_trait.as_ref()?;
1281 Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
1284 pub(crate) fn return_type_impl_traits(
1285 db: &dyn HirDatabase,
1286 def: hir_def::FunctionId,
1287 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1288 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1289 let data = db.function_data(def);
1290 let resolver = def.resolver(db.upcast());
1291 let ctx_ret = TyLoweringContext::new(db, &resolver)
1292 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1293 .with_type_param_mode(TypeParamLoweringMode::Variable);
1294 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1295 let generics = generics(db.upcast(), def.into());
1296 let num_binders = generics.len();
1297 let return_type_impl_traits =
1298 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1299 if return_type_impl_traits.impl_traits.is_empty() {
1302 Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))
1306 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1308 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1309 hir_def::type_ref::Mutability::Mut => Mutability::Mut,